In a Sunday interview with BBC, Home Secretary Amber Rudd said some involved in the incident, which killed 22 people, could still be at-large.

“The intelligence services are still collecting information about (Abedi) and about the people around him,” she said. “What this reminds us is the scale of the problem that we have, the enemy that we have, Daesh, that is trying to weaponize the young people in our society.”

The following image captured by a public surveillance camera shows Salman Abedi shortly before carrying out the attack at an Ariana Grande concert Monday evening:

(courtesy Greater Manchester Police via BBC News)

UPDATE — 6:04 p.m. EDT: UK’s National Police Chiefs’ Council announced late Thursday that British intelligence is again being shared with the U.S., following “fresh assurances”, presumably from American officials.

In related news, a CNN source described only as a U.S. official told the American network that suicide bomber Salman Abedi was most likely trained by ISIS during the 22-year-old’s time in Syria prior to his recent return to England.

Secretary of State Rex Tillerson is scheduled to meet with British Foreign Secretary Boris Johnson in the UK on Friday.

Greater Manchester Police took two men, a seventh and eighth suspect, into custody Thursday as its investigation into Monday evening’s suicide bombing at the Manchester Arena expanded.

Officials say the two additional persons of interest were arrested following police sweeps of the Greater Manchester area. Local authorities called the arrests “significant.”

“I think it’s very clear that this is a network that we are investigating. And as I’ve said, it continues at a pace. There’s extensive investigations going on and activity taking place across Greater Manchester as we speak,” Greater Manchester Police chief Ian Hopkins told reporters Wednesday.

Carried out by Salman Abedi, who detonated an explosive device in an entrance hallway of the arena, Monday’s attack killed 22 and injured over 116 concert goers attending an Ariana Grande concert. 75 people remain hospitalized; an additional 23 remain in critical condition.

The Islamic State (ISIS) has claimed responsibility for the terror attack.

A ninth person of interest, a woman, was briefly detained Wednesday, but released later in the day.

Authorities say one of the two men arrested, Ismail Abedi, is the older brother of suicide bomber Salman. Greater Manchester Police did not release the name of the eighth man in custody.

Police also say the eighth unidentified man was arrested outside central Manchester was spotted carrying a package when taken into custody.

The arrests on Wednesday in the United Kingdom are on top of the arrests of Ramadan and Hashim Abedi, the father and older brother of the bombing suspect Salman Abedi by Libyan security officials in Tripoli, Libya.

Libyan security officials say both men were aware of “all the details” of the Manchester attack.

As details related to Monday’s attack emerged, some of which were apparently leaked from American media outlets, British counter-terrorism officials have temporarily halted sharing information with U.S. intelligence services over concerns the excessive disclosures would damage the inquiry.

Multiple media outlets are reporting the revelations have caused alarm and British Prime Minister Theresa May will address the matter with President Trump at a NATO meeting in Brussels later on Thursday.

Following May’s comment that “intelligence that is shared between law enforcement agencies must remain secure,” AP reported Trump issued a statement pledging to “get to the bottom” of the leaks and called on the Justice Department to investigate the matter and “if appropriate, the culprit should be prosecuted to the fullest extent of the law.”